Abstract
Many approaches have been used to investigate climate change impacts on agriculture. However, several caveats remain in this field: (i) analyses focus only on a few major crops, (ii) large differences in yield impacts are observed between projections from site-based crops models and Global Gridded Crop Models (GGCMs), (iii) climate change impacts on livestock are rarely quantified, and (iv) several causal relations among biophysical, environmental, and socioeconomic aspects are usually not taken into account. We investigate how assumptions about these four aspects affect agricultural markets, food supply, consumer well-being, and land use at global level by deploying a large-scale socioeconomic model of the global economy with detailed representation of the agricultural sector. We find global welfare impacts several times larger when climate impacts all crops and all livestock compared to a scenario with impacts limited to major crops. At the regional level, food budget can decrease by 10 to 25% in developing countries, challenging food security. The role of land area expansion as a major source of adaptation is highlighted. Climate impacts on crop yields from site-based process crop models generate more challenging socioeconomic outcomes than those from GGCMs. We conclude that the agricultural research community should expand efforts to estimate climate impacts on many more crops and livestock. Also, careful comparison of the GGCMs and traditional site-based process crop models is needed to understand their major implications for agricultural and food markets.
Generated Summary
This research investigates the economic impacts of climate change on global agricultural markets. The study employs a large-scale socioeconomic model of the global economy, incorporating detailed representations of the agricultural sector. The primary aim is to assess how assumptions about crop selection, yield impacts, livestock productivity, and various socioeconomic aspects affect agricultural markets, food supply, consumer well-being, and land use at the global level. The methodology involves comparing results from traditional regional-scale studies using site-based models (IPCC) with global-scale results from Global Gridded Crop Models (GGCMs). Furthermore, the study extends these impacts to include pasture yields and livestock productivity, providing a sensitivity analysis to establish the priority the research community should place on estimating climate impacts on a more comprehensive set of agricultural commodities. The study uses the MIT Emissions Prediction and Policy Analysis (EPPA) model, a recursive-dynamic multi-regional and multi-sectorial computable general equilibrium (CGE) model, and applies climate shocks on crop yields and livestock productivity into the economic model, based on climate impacts on crops and livestock by the IPCC and simulation of crop yields using GGCMs crop emulators. The research also focuses on environmental metrics, including land use changes and CO2 emissions from land, to evaluate the overall impacts of climate change.
Key Findings & Statistics
- The study highlights that global welfare impacts are six to 13 times larger when climate impacts directly affect all crops and livestock, compared to scenarios where only rice, maize, soybean, and wheat are affected.
- Food budget impacts are around 3% or less when only crops are directly affected, but increase to 10% to 25% in developing countries when climate change impacts all crops and livestock commodities.
- Global production of maize, wheat, rice, and soybeans was worth approximately 800 billion US dollars in 2016, which accounted for only about 17% of the total value of all agricultural products.
- Studies indicate a current loss in the US of about $1.7 to $2.4 billion due to heat stress in the dairy and beef industry.
- The comparison between IPCC and GGCM projections from Rosenzweig et al. (2014) differs from these results due to differences in methodology (mean vs. median impacts, different regional delineations, and categorization of GGCMs with and without explicit nitrogen stress).
- The IPCC scenarios show many more regions with negative impacts.
- In the IPCC Crops & Livestock scenario, some crop and livestock outputs decrease by more than 5%.
- Under the IPCC scenarios, crop prices tend to increase above the BAU, rising in the range of 10 to 30% by 2050 from their 2015 levels.
- When climate impacts are imposed only on RMSW crops, agriculture outputs deviate less than 1% from the BAU projections in 2050.
- The Other Crop price index rises higher (by as much as 50%) above 2015 levels, reflecting the greater increase in the BAU.
- In the IPCC Crops & Livestock scenario, there is a large increase in pasture and a small increase in cropland, at the expense of managed forest.
Other Important Findings
- The research identifies several caveats in climate change impact assessment: analyses often focus on a few major crops; large differences in yield impacts are observed between site-based models and GGCMs; climate change impacts on livestock are rarely quantified; and socioeconomic aspects are often not considered.
- The study emphasizes the importance of considering a wider range of crops and livestock in climate impact assessments, as focusing on a few major crops can be misleading.
- The study reveals that the choice of climate models (site-based vs. GGCMs) significantly affects the outcomes, with site-based models potentially generating more challenging socioeconomic outcomes.
- The research points out that a key adaptation mechanism is land area expansion.
- The study indicates that regional impacts on output depend on yield changes relative to the global average, with production shifting toward regions less negatively affected.
- The research highlights that land use changes and CO2 emissions show complex effects, varying with the inclusion of direct impacts on crops and livestock.
- The study suggests that the expansion of land area devoted to a commodity’s production is a major source of adaptation and that heterogeneous climate impacts on crops would promote relevant shifts among crops.
Limitations Noted in the Document
- The study acknowledges that the complexity and data requirements of crop models make large-scale simulations expensive, often limiting the number of sites used to represent a region.
- The representativeness of the few sites used in site-based models may be questionable.
- The study recognizes that the assumption of extending average impacts to all crops and livestock is a simplification and a form of sensitivity analysis.
- The research notes the need for caution when comparing median effects from different climate models, particularly GGCMs, due to the wide range of impacts and potential for offsetting effects.
- The study points out that a family of crop models applied to different crops gives somewhat similar yield changes.
- The difficulty in arriving at quantification is that there are not straightforward relationships that can be applied at the regional or global level, or how effects vary by breed, management approach, and the effectiveness and cost of adaptive measures such as mist cooling, shade, and fans.
Conclusion
The study emphasizes the crucial need to broaden the scope of climate impact assessments on agriculture by including a wider range of crops and livestock, along with a more detailed examination of the various socioeconomic aspects. It highlights the significant underestimation of climate impacts when only a few major crops are considered, underscoring the need for comprehensive analyses that account for the interconnectedness of agricultural commodities and the global markets. The analysis of land use changes underscores the importance of adaptation strategies and the potential risks to biodiversity and carbon emissions if land management is not appropriately addressed. The study also highlights the limitations of the current crop modeling exercises, particularly in terms of their representation of regions and the need for more detailed and spatially resolved data. The findings call for a reevaluation of existing approaches to climate impact assessment and policy formulation, urging a more inclusive and nuanced approach that incorporates the full complexity of agricultural systems. Furthermore, the research emphasizes the importance of understanding how regional effects translate into global outcomes, highlighting the need for further research and policy discussions to adapt to the challenges posed by climate change.